(a) Field of the Invention
The present invention pertains to a compound transistor circuit consisting of a combination of bipolar transistors, and more particularly it relates to a compound transistor circuit of bipolar transistors which requires no or negligible amount of input or offset current for operation.
(b) Description of the Prior Art
There has been desired a transistor having a high input impedance as well as a high gain, to make it possible to easily materialize an amplifier circuit of a simple arrangement which provides a high gain and a high input impedance. The existing transistors such as bipolar transistors and field effect transistors, however, cannot fully meet these requirements, for the following reasons.
A bipolar transistor has the disadvantage that its input impedance is fairly low since it requires a considerable amount of input and offset currents for operation. In contrast thereto, a field effect transistor is superior to a bipolar transistor with respect to the input impedance requirement, but on the other hand, its possible gain, in general, is quite poor as compared with a bipolar transistor.